To: J3                                                      08-307
From: John Reid
Subject: Pointer components and coindexed arguments
Date: 2008 Nov 17
References: J3/08-007r2 (WG5/N1723), 08-216r2, 08-282


Discussion

This is a revision of 08-216r2 following the comments in 08-282.

It is made clear (157: 7.2.2.3, para 2) that for data pointer
assignment, if the <data target> is a pointer with a target that is
not on the same image, the pointer association status of the
<pointer-data-object> becomes undefined. Note 7.46 explains that this
is intended to cover situations where data pointer association with a
target that is not on the same image might otherwise be implied. While
the intention is clear, the normative text does not cover situations
that are not defined in terms of pointer assignment, notably when a
coindexed actual argument has a pointer component.

To cover all situations, we think that it should be made clear in
16.5.2 that a data pointer can be associated only with a target that
is on the same image.

We also propose to add to 16.5.2.5 the case of a pointer component of
a coindexed actual argument to the list of ways that the association
status of a pointer may become undefined.

We also propose to expand Note 7.46.

Edits to J3/08-007r2 (WG5/N1723):

[157:Note 7.46] In 7.2.2.3 "Data pointer assignment", in the Note
following para 2, second sentence, replace "This prevents this
statement" with "This prevents a pointer assignment statement from".

[157:Note 7.46] In 7.2.2.3 "Data pointer assignment", in the Note
following para 2, third sentence, delete the middle clause ", such as
...  intrinsic assignment". Then add a new final sentence, "Examples
include a pointer component in a derived-type intrinsic assignment or
a pointer component of an allocate object in an ALLOCATE statement if
SOURCE= appears and the source expression is coindexed."

[288] In 12.5.2.3 "Argument association", para 5, after "pointer
actual argument" add "that is not a subobject of a coindexed object".

[288] In 12.5.2.3 "Argument association", after para 5 add a new para:
"If the actual argument is a coindexed object having a pointer
subobject, the corresponding subobject of the dummy argument is not
associated with the target of the actual argument subobject. On entry
to the procedure, the pointer association status of the subobject of
the dummy argument becomes undefined; on return from the procedure,
the pointer association status of the subobject of the actual
argument becomes undefined unless the dummy argument has INTENT(IN)"

[446] In 16.5.2.1 "Pointer association / General", para 1, line 2,
after "different targets" add "on its own image".

[448] In 16.5.2.5 "Events that cause the association status of
pointers to become undefined" remove "or" at the end of item (11),
change the final period at the end of (12) to a comma, and add to the
list:

"(13) a procedure is invoked with the pointer as a data pointer
subobject of a dummy argument that corresponds to an actual argument
that is a coindexed object, or

(14) return takes place from a procedure with the pointer as a
data pointer subobject of an actual argument that is a coindexed
object corresponding to a dummy argument that is not of INTENT(IN)."